This invention relates to microwave moisture sensing arrangements.
In Y. Miyai "A New Microwave Moisture Meter for Grains", J. Microwave Power 13(2), 1978 is described a microwave moisture meter for grains using a hybrid microwave integrated circuit (MIC) and a strip line sensor which measures the microwave attenuation due to the measure of the moisture content of grain passing over the sensor.
The Miyai instrument is comprised in a casing adapted for installation in a window made in the wall of a hot-air dryer in which rice grains are circulated on a conveyor. A sensor plate incorporating the strip line sensor is on one wall of the casing and is placed against the window so that the rice grains flow over it.
Such an arrangement is useful only where flowing materials are being monitored, and was devised in particular for automatic operation of the rice-grain drying process.
There are many instances, however, where moisture content in static, penetrable materials needs to be measured. The Miyai instrument is quite unsuited to such measurements.
The present invention provides a microwave moisture sensing arrangement which is especially adapted to such measurements and is useful in a wide variety of circumstances and for measuring moisture in a wide variety of materials as well as being adapted for use as a level sensor.